In some firearms with a rotating bolt that locks the bolt to the barrel, for example the M16 family of weapons, there are problems with extracting fired cases from the firing chamber. This problem arises when the bolt group rotates to unlock and start moving rearwards, as there is a centrifugal spin force created which can cause the extractor of the bolt group to move or spin off of the empty cartridge case rim and hence cause a failure to extract the empty cartridge casing. The high recoil velocity of the bolt also overcomes the spring force of the extractor which causes the extractor to lift off the case rim.
For the M16 weapon family, various solutions have been proposed to solve the extraction failure problem. These solutions generally involved decreasing of the power drive of the operating group. For example, larger gas tubes have been proposed to slow the extraction time and hence to reduce the centrifugal force. However, this proposed solution was disadvantageous since the larger gas tubes decreased the rate of fire and had function problems in cold weather.
Another proposed solution was the use of different drive springs. While this resulted in a slower extraction and hence less centrifugal force, this proposed solution was disadvantageous since it created short recoils. The bolt group does not move rearward enough to strip the next live round to be fired. The heavy drive spring also creates bolt bounce which prevents the firing pin from contacting the primer of the cartridge.
The use of heavy buffer weights as a solution to the extraction problem was also proposed. However, such buffer weights created short recoils which prevents the operating group from stripping the next round out of the magazine.
Still another proposed solution was to use different extractor springs.
However, smaller extractor springs resulted in failures of the extractor to snap on the cartridge rim.
Thus, a solution which provided a reliable extractor which did not adversely effect the firing rate was desired for rotating bolt groups.
In accordance with the present invention, an apparatus is provided for initially slowing a backwards extraction movement of a bolt group of a weapon firing a projectile. This bolt group moves backward automatically after firing of the projectile, against a force of a return drive spring. The apparatus includes a first longitudinal member having a first distal end and a first proximal end and a second longitudinal member having a second distal end adjacent the first proximal end and a second proximal end. A mounting means is provided for mounting the first and second members for longitudinal movement of the first member relative to the second member and adjacent the drive spring, with the drive spring urging the first and second members apart and opposing the extraction movement of the bolt group. A retarding means is then provided for retarding an initial backwards movement of the first proximal end relative to the second distal end, and also for allowing a relatively free further backwards movement of the first proximal end relative to the second distal end as the bolt group moves backwards after firing.
In a preferred embodiment, the mounting means includes a third longitudinal member having a third distal end and a third proximal end. The mounting means mounts the second and third members for longitudinal movement of the second member relative to the third member and adjacent the drive spring, with the drive spring urging the second and third members apart and against the bolt group. In addition, a latch means is provided for releasably latching the second proximal end to the third distal end. This latch means includes a release member which is contacted when the first proximal end approaches the second proximal end to release the latching of the second proximal end to the third distal end.
In the preferred embodiment, the retarding means includes a hydraulic chamber inside of the second member which is filled with a hydraulic fluid. A longitudinally short, inwardly reduced wall section of the chamber is then provided adjacent the second distal end, and a piston head at the first proximal end is initially disposed at the reduced wall section. The piston head is sized to pass along the reduced wall section with a movement which is retarded by the passage of the hydraulic fluid thereabout. Then, after the piston head passes the reduced wall section, the piston head easily passes along a remainder of the hydraulic chamber as the hydraulic fluid passes easily about the piston head and a remainder wall section of the chamber.
Also in the preferred embodiment, the first longitudinal member is a piston member which is disposed inside of the drive spring. This piston member includes an elongate piston rod with the piston head provided at the first proximal end, and an enlarged piston stop provided at the first distal end against which a first end of the drive spring is engaged. In addition, the second longitudinal member is a cylinder member disposed inside of the drive spring which has the chamber disposed therein. Further, the third longitudinal member is a buffer guide disposed inside of the drive spring which telescopically receives the second proximal end of the cylinder member. The buffer guide includes an enlarged buffer stop at the third proximal end against which a second end of the drive spring is engaged.
Further in the preferred embodiment, the release member is contacted by the piston head to release the second proximal end from the third distal end so that the second proximal end is then received in the buffer guide. In addition, the release member is spring biased towards the piston head and includes a camming surface. The latch means then includes a pair of latch members having oppositely directed shoulders which engage the third distal end of the buffer guide. The latch members also include inwardly directed latch distal cams which slide along the camming surface of the release member and inwardly directed latch proximal cams. The latch members are each pivotally mounted to the second proximal end. The release member includes a release proximal end which contacts the inwardly directed latch proximal cams as the release member is moved proximally, such that the latch members are pivoted to positively move respective shoulders from engagement with the third distal end.
It is an advantage of the present invention that a rotating bolt group with a reliable extraction operation is provided.
It is also an advantage of the present invention that, together with reliable extraction of the empty cartridge case effected with an initial retarding of the extraction movement, there is no appreciable decrease in the firing rate of the weapon attributable to the retarding.
It is a further advantage that the apparatus of the present invention fits within the confines of the prior art drive spring or drive spring compartment.
Other features and advantages of the present invention are stated in or apparent from detailed descriptions of presently preferred embodiments of the invention found hereinbelow.